President Obama's executive decision to grant immunity to a select group of undocumented immigrants is provoking hostility from Republicans, much to the delight of Democrats. The president is already enjoying gains among Hispanics in polling, and his campaign has reason to hope the fallout will clarify to this key voting bloc which candidate is on their side ahead of the election.

For Mitt Romney, the chasm between Hispanics and his anti-immigration conservative base is already proving to be unbridgeable -- and it's only growing.

In floor speeches and media appearances Monday, House Republicans channeled the misgivings of conservatives, excoriating Obama's policy decision as an "imperial" move that shows a lack of respect for the rule of law. At least one member of Congress has already threatened to sue to block it.

Although the prime directive from GOP leaders has been to focus on the process and timing of Obama's administrative shift, it has been difficult for some rank-and-file members to refrain from going after the substance. For instance, Rep. Blake Farenthold (R-TX) argued that some minors brought to the U.S. by their parents knowingly broke the law and should be held accountable.

"Well, you are also talking about people that came over at 16 years of age," Farenthold told CNN. "At that point you had a say in it and that looks more like amnesty."

Here's a highlight reel of Republican push-back against the new policy.

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Romney has so fardodged the substance of Obama's decision, which opens the door to two-year work authorization for illegal immigrants under 30 who were brought to the U.S. as children and meet certain criteria, such as having attained higher education or serving in the military. He has refused to say if he'd reverse the decision as president, which he's already facing pressure from the right to pledge to do.

Romney's former opponent and now-surrogate Rick Santorum said Sunday that his party's nominee is "trying to walk the line" on the issue so as to avoid appearing "hostile" to Latinos.

Even Sen. Marco Rubio (R-FL), who has recently championed the cause of granting legal status to DREAM Act-eligible immigrants, has felt compelled to hedge on Obama's shift.

Meanwhile, Obama is already enjoying a boon among Latino voters, who comprise the nation's fast-growing demographic and have been disillusioned by the lack of immigration relief that has occurred during his presidency. His decision has fueled a 35 percent net gain in Hispanic enthusiasm behind his candidacy, according to a Latino Decisions survey.

For Romney, losing Latino voters -- or mobilizing unenthusiastic Hispanics to pull the lever against him -- could potentially be fatal in swing states. It's a delicate balance for the Republican nominee, whose record of moderate positions as governor of Massachusetts means he cannot take the enthusiasm of his right-wing base for granted.